The Drosophila laboratory is currently engaged in serveral attacks on each of two different problems -- the genetic control of meiosis and the genetic organization of heterochromatin. With respect to meiosis, the major approaches include: (1) an electron and light microscopical study of meiosis in males carrying the disjunction-defective meiotic mutants pal, ord, an mei-S332; (2) the collection of new autosomal meiotic mutants; (3) the analysis of a newly discovered recombination-enhancing meiotic mutant; (4) an examination of the influence of recombination-defective meiotic mutants on recombination of the influence of recombination-defective meiotic mutants on recombination in heterozygotes for various chromosomal aberrations. With respect to heterochromatin: (1) the genetics and embryology of mutants in the da -abo region is being studied; (2) effects of specific heterochromatin on compound-X chromosome behavior have been discovered and are being analyzed; (3) specific heterochromatic regions that interact to cause lethality are being elucidated.